Enhancing microalgae-based bioremediation technologies with carbon-coated zero valent iron nanoparticles

This study investigated the influence of the addition of carbon-coated zero-valent nanoparticles to enhance CO2 removal efficiency, contributing to improved microalgae growth and biogas upgrading. NPs were studied in different formats - raw suspension (Raw-NPs) and dried format (D-NPs)-, along with the liquid fraction of the raw suspension (SP) on the performance of Chlorella sorokiniana for biogas upgrading and domestic wastewater treatment. The supplementation of SP at increasing concentrations during biogas upgrading resulted in higher CO2 levels and microalgae inhibition. The addition of dried NPs enhanced microalgae growth but did not foster CO2 absorption or biomethane quality regardless of their concentration (CO2: 0.3–0.8 %; CH4 69–73 %). Similarly, higher microalgae growth and photosynthetic activities were recorded at increasing dried NP concentrations during domestic wastewater treatment. The addition of D-NPs resulted in removal efficiencies of 74 %, 49 %, and 90 % for IC, TN and ammonium, respectively.